This section provides background information related to the present disclosure which is not necessarily prior art.
Exhaust aftertreatment systems may include a diesel particulate filter for treating the exhaust of a diesel engine. In many applications, it may be beneficial to periodically regenerate or oxidize soot trapped within the diesel particulate filter. A regeneration device such as a burner may be positioned upstream of the diesel particulate filter. The burner is typically provided with a fuel such as a hydrocarbon, a supply of oxygen and one or more igniters. Combustion of the fuel within the burner increases the energy of the exhaust entering the diesel particulate filter. Oxidation of the soot trapped within the filter occurs during the regeneration process.
Some vehicles are equipped with compressors associated with engine superchargers or turbochargers. In some instances, the output from the compressor provides a secondary air supply to a nozzle useful for atomizing the fuel within the regeneration device. Because the compressor output is typically directly related to engine speed, the flow of compressed air to the nozzle varies greatly during engine operation. As such, an exhaust aftertreatment system properly designed for operation at relatively low to moderate engine speeds may not optimally function at an upper range of engine speeds.
For example, at high engine speeds, the output flow rate from the compressor is high. The resistance to air flow through the nozzle of the burner may be significant. A resistance to flow at the outlet of the compressor may undesirably load the compressor and increase the operating temperature of the compressor. Control systems may be required to assure that the compressor temperature does not exceed a predetermined maximum temperature. A maximum output pressure may be set. By limiting the compressor output, the flow rate of secondary air through the burner nozzle may be insufficient to heat the high volume of exhaust flowing through the burner. An undesirably low temperature at the diesel particulate filter inlet may result. Therefore, a need in the art may exist to provide a modified secondary air system for use with an exhaust gas aftertreatment system.